Quantum Computing is still many years away, however, a new paper published on 20 August in Nature Photonics has just made a huge leap towards turning the concept into reality (1). The paper presents the proof-of-concept for a fully programmable two-qubit quantum processor that enables “universal two-qubit quantum information processing in optics.”
The new chip is made up of more than 200 photonic components and uses complementary metal-oxide semiconductors, and is capable of performing delicate quantum information experiments with 100,000 different reprogrammable settings. Moreover, according to the report, the processor can “implement 98 different two-qubit unitary operations” at a 93% efficiency.
Up to now, only quantum processes using a single qubit have been able to with high precision. One of the major stumbling blocks of quantum computing has been adding a second qubit and thus enabling quantum entanglement, which according to the team led by Xiaogang Qiang from the Quantum Engineering Technology Labs at the University of Bristol in the UK “is recognised as one of the most challenging tasks for photonics because of the extra resources required for each entangling step.”
In quantum mechanics, light and matter exhibit properties of both waves and of particles, a concept that has presented some perplexing ideas, like the notion that physical properties, such the position of an electron, don’t really exist until they are observed. But these baffling theories have now become the basic blueprint for quantum computing, which was first proposed in the 1980s.
Digital computers use data encoded into binary digits, called bits, and each bit is always in one of either two definite states (0 or 1). On the other hand, quantum bits or qubits can also exist in another mode called a superposition, which gives them unique and powerful properties, thereby allowing them to do much more than conventional bits. Some practical examples include superconducting circuits or individual atoms levitated inside electromagnetic fields. The potential for quantum computers to use a collection of qubits in superpositions to explore different possible paths through a calculation is what would allow them to find solutions in fewer steps than conventional computers.
One of the reasons quantum computers still remain a futuristic fantasy is that qubits control extremely sensitive quantum processes but are incredibly temperamental. Therefore, any physical disturbances, including heat and noise, can easily alter the 0s and 1s, or undo critical superpositions. Thus, a considerable portion of a quantum processor would be required to correct for misfiring qubits.
This newest accomplishment is an exciting step toward a new era of quantum computing. Big tech companies such as Google, Intel, Microsoft, and IBM have started to invest heavily in quantum technology, alluding to its undeniable potential, and there are a growing number of startups exploring the technology. As the arduous race to the finish line continues, savvy investors will be keeping their eye on the prize.
Quantum technology probably won’t be making it into your smartphone anytime soon, but if scientists can pull off this amazing feat, we could be seeing longer-lasting batteries for electric cars or advances in chemistry that could redefine industries, or maybe even advance code-breaking capabilities.
(1) Qiang, X. et al. Large-scale silicon quantum photonics implementing arbitrary two-qubit processing. Nature Photonics (2018). DOI: 10.1038/s41566-018-0236-y
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